This invention relates to stents and a method for retrieving stents after insertion into the body of a patient. In particular, the invention relates to modifications to the Gianturco Expandable Wire Stent.
It is desirable in various situations to provide means for expanding a constricted vessel portion or for maintaining an open passageway through a vessel portion. Such situations arise, for example, in conjunction with arteriosclerosis that restricts or stops blood flow through a vessel, or in conjunction with diseases of the prostrate gland which resrict or stop flow through the urethra.
A percutaneous stent developed by Dr. Cesare Gianturco is formed of a stainless steel wire arranged in a closed, zig-zag pattern, as more fully described in U.S. Pat. No. 4,580,568. The Gianturco stent, or the Z-stent as it is also known, is compressed into a reduced size shape with an outer diameter which is many times smaller its outer diameter in an expanded shape. The stent is positioned in a passageway by means of a sheath while the stent is retained in the compressed reduced size shape. A pusher or flat-ended catheter is used through the sheath to hold the stent in place in the passageway while the sheath is withdrawn, thereby allowing the stent to expand in the passageway into its expanded shape to hold the passageway open and enlarged. Thus, the Z-stent provides a self-expanding means for maintaining an open passageway. FIG. 1 illustrates the use of the well-known Z-stent wire within a body passageway.
FIG. 2 illustrates the use of several Z-stents along a limited length of a body passageway. In illustrated arrangement, two stents are situated in an overlapping arrangement, while a third stent is disposed slightly downstream from the other two stents. As discussed more fully in the above-referenced Gianturco '568 patent, each of the three stents must be separately inserted using the sheath and pusher described above.
Since the initial development of the expandable wire Z-stent, it has been discovered that over time a Z-stent may continue to expand to its maximum diameter even though it was originally deployed in a passageway that had a diameter somewhat smaller than the maximum outer diameter of the expanded stent. Thus, the end result has been in some cases that the stent becomes embedded deeply into the walls of the passageway. In an effort to address this particular problem, others in the art have modified the expandable Z-stent to form eyes at the bends or joints of the zig-zag configuration. A monofilament line is then threaded through each of the eyes at one end of the stent to form, in essence, a continuous flexible ring which restricts the expansion of the wire stent. The monofilament line is sufficiently elastic in the tensile direction to control the expansion of the stent to an optimal desired diameter.
Further description of this modified expandable wire Z-stent is found in the following references:
Modified Gianturco Expandable Wire Stents in Experimental and Clinical Use, J. Rosch, CIRSE, Porto Cervo, Sardinia, May 25-29, 1987, Vol 31-No. 2, 1988 PA1 Modifications of Gianturco Expandable Wire Stents, Barry T. Uchida, AJR 150:1185-1187, May 1988, American Roentgen Ray Society PA1 Experimental Intrahepatic Portacaval Anastomosis: Use of Expandable Gianturco Stents, Josef Rosch, M.D., RSNA, 1987, Volume 162 No. 2 PA1 Superior Vena Cava Syndrome Associated with Massive Thrombosis: Treatment with Expandable Wire Stents, RSNA, June 1988 PA1 Gianturco Expandable Wire Stents in the Treatment of Superior Vena Cava Syndrome Recurring After Maximum-Tolerance Radiation, Reprinted from CANCER, Vol. 60, No. 6, Sept. 15, 1987.
There remains, however, a need for a percutaneous stent that is self-expanding, yet can be retrieved after a period of time of insertion. There is also need for a percutaneous stent that includes several stent sections for insertion along a greater length of a body passageway than has been permitted by expandable stents of the prior art. There is also a need for a stent capable of combination with multiple stent sections that does not require multiple catheterizations for insertion operations.